This study attempts primarily to develop a simple instrument, empirically produced for the identification of mothers at risk of delivering a LBW infant. Longitudinal data are available for selecting variables at different points during pregnancy. Sample size of the total population is 17,000. The risk score is developed in a random sample of 8000 patients and tested in the remaining group. Furthermore, the following projects are performed using this source of data: - Epidemiology of subgroups of IUGR infants and their neonatal morbidity (paper submitted). - Physical activity and work during pregnancy and pregnancy outcome (paper submitted). - Protozoan and helminthic infections during pregnancy and its effect on birth weight (paper submitted). - Lactose malabsorption during pregnancy: A longitudinal study (paper published). - Body composition and physical activity during pregnancy and birth weight (paper submitted).